netdev - Re: [PATCH net-next] openvswitch: Make metadata_dst tunnel work in IP_TUNNEL_INFO

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Message-ID: <CAOrHB_B27dKTqvb08DPnA1u0Mc=hV+jWr8W5uTajip8gi+9Dsg@mail.gmail.com>
Date:   Mon, 25 Mar 2019 12:22:34 -0700
From:   Pravin Shelar <pshelar@....org>
To:     wenxu <wenxu@...oud.cn>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH net-next] openvswitch: Make metadata_dst tunnel work in
 IP_TUNNEL_INFO_BRIDGE mode

On Sun, Mar 24, 2019 at 6:24 PM wenxu <wenxu@...oud.cn> wrote:
>
> On 2019/3/25 上午2:46, Pravin Shelar wrote:
> > On Sun, Mar 24, 2019 at 12:03 AM wenxu <wenxu@...oud.cn> wrote:
> >> On 2019/3/24 上午5:39, Pravin Shelar wrote:
> >>> On Sat, Mar 23, 2019 at 2:18 AM wenxu <wenxu@...oud.cn> wrote:
> >>>> On 2019/3/23 下午3:50, Pravin Shelar wrote:
> >>>>
> >>>> On Thu, Mar 21, 2019 at 3:34 AM <wenxu@...oud.cn> wrote:
> >>>>
> >>>> From: wenxu <wenxu@...oud.cn>
> >>>>
> >>>> There is currently no support for the multicasti/broadcst aspects
> >>>> of VXLAN in ovs. In the datapath flow the tun_dst must specific.
> >>>> But in the IP_TUNNEL_INFO_BRIDGE mode the tun_dst can not be specific.
> >>>> And the packet can forward through the fdb of vxlan devcice. In
> >>>> this mode the broadcast/multicast packet can be sent through the
> >>>> following ways in ovs.
> >>>>
> >>>> ovs-vsctl add-port br0 vxlan -- set in vxlan type=vxlan \
> >>>>         options:key=1000 options:remote_ip=flow
> >>>> ovs-ofctl add-flow br0 in_port=LOCAL,dl_dst=ff:ff:ff:ff:ff:ff,\
> >>>>         action=output:vxlan
> >>>>
> >>>> bridge fdb append ff:ff:ff:ff:ff:ff dev vxlan_sys_4789 dst 172.168.0.1 \
> >>>>         src_vni 1000 vni 1000 self
> >>>> bridge fdb append ff:ff:ff:ff:ff:ff dev vxlan_sys_4789 dst 172.168.0.2 \
> >>>> src_vni 1000 vni 1000 self
> >>>>
> >>>> This would make datapath bit complicated, can you give example of such use-case?
> >>>>
> >>>> There is currently no support for the multicast/broadcast aspects
> >>>> of VXLAN in ovs. To get around the lack of multicast support, it is possible to
> >>>> pre-provision MAC to IP address mappings either manually or from a controller.
> >>>>
> >>>> With this patch we can achieve this through the fdb of the lower vxlan
> >>>> device.
> >>>>
> >>>> For example. three severs connects with vxlan.
> >>>> server1 IP 10.0.0.1 tunnel IP  172.168.0.1 vni 1000
> >>>> server2 IP 10.0.0.2 tunnel IP  172.168.0.2 vni 1000
> >>>> server3 IP 10.0.0.3 tunnel IP  172.168.0.3 vni 1000
> >>>>
> >>>> All the broadcast arp request from server1, can be send to vxlan_sys_4789
> >>>> in IP_TUNNEL_INFO_BRIDGE mode. Then the broadcast packet can send through
> >>>> the fdb table in the vxlan device as following:
> >>>>
> >>>> bridge fdb append ff:ff:ff:ff:ff:ff dev vxlan_sys_4789 dst 172.168.0.1 \
> >>>>         src_vni 1000 vni 1000 self
> >>>> bridge fdb append ff:ff:ff:ff:ff:ff dev vxlan_sys_4789 dst 172.168.0.2 \
> >>>> src_vni 1000 vni 1000 self
> >>>>
> >>>>
> >>>> Not any for multicast case. This patch make ovs vxlan tunnel using the fdb
> >>>> table of lower vxlan device.
> >>> Have you tried OVS mac learning?
> >>>
> >> The key point is that it makes ovs vxlan tunnel can make use of the fdb table of lower vxlan device.
> >>
> >> The fdb table can be configurable or mac learning from outside.
> >>
> >> For the broadcast example.  In the ovs, it can only achieve this through multiple output actions to simulate the broadcast.
> >>
> >> ovs-ofctl add-flow br0 in_port=server1,dl_dst=ff:ff:ff:ff:ff:ff,actions=set_field:172.168.0.1->tun_dst,output:vxlan,\
> >>
> >>     set_field:172.168.0.2->tun_dst,output:vxlan.
> >>
> >> But there are some limits for the number of output actions.
> >>
> > I was referring to mac-learning feature in OVS i.e. using learn
> > action. I wanted to see if there is something that you are not able to
> > do with OVS learn action.
> >
> Ovs mac learn action is only work for the specific vxlan tunnel port（ fixed tun_dst, tun_id) like following.
>
> ovs-vsctl set in vxlan options:remote_ip=172.168.0.1 options:key=1000
>
> ( This is the same problem for Linux bridge, It achieve this through IP_TUNNEL_INFO_BRIDGE mode work
>
> with the fdb of lower vxlan device)
>
>
> But it is not work for the flow based tunnel (remote_ip=flow),  There will be huge number of the tunnel peer.
>
> It' hard to manage the tunnel port with the specific mode.
>
>
OK, So it is hard to use ovs learn action, but it is doable. Given
IP_TUNNEL_INFO_BRIDGE is not adding too much complexity to OVS, I am
fine adding this feature.

Thanks.